A Nigerian girl who staged a remarkable escape when gunmen took her and more than 200 others hostage has described how she was told: "Don't worry, we're soldiers. Nothing is going to happen to you."

The 16-year-old was snatched from her boarding school in Chibok by members of the Islamic group Boko Haram. She was herded into a pick-up truck and driven away but fled when one of the vehicles in the convoy broke down.

She and her friends jumped down from the truck and darted into a nearby forest to hide when the stranded car behind them suddenly started up, illuminating the road ahead.

"We ran and ran, so fast," said the girl. "That's how I saved myself. I had no time to be scared. I was just running."